1. Field of the Invention
The present invention relates to magnetic head positioner assembly for use in disk storage systems such as magnetic or optical disk storage systems.
2. Description of the Related Art
The density of storage of data in magnetic disk units are now increasing at an annual rate of 60% or more due to an improvement in BPI (Bit Per Inch) and TPI (Track Per Inch).
To realize a higher BPI, required are a reduction in height at which magnetic heads fly over the disk surface, the employment of highly sensitive heads, and highly efficient signal processing techniques. To realize a higher TPI, a technique for positioning magnetic heads with high accuracy is inevitable in addition to the foregoing.
For example, a density of storage of data of 0.155 Gb/cm2 (1 Gb/in2) provides densities of 8 kTPI or less in the direction of tracks or track pitches of 3 to 4 xcexcm. To realize a density of storage of data of 1.55 Gb/cm2 (10 Gb/in2) or greater, track densities of 25 kTPI or greater or track pitches of 1 xcexcm or less are required. This in turn requires an accuracy of positioning of magnetic heads on the disks of 0.1 xcexcm or less (which is approximately equal to 10% of a track pitch).
FIG. 1 is a perspective view showing a conventional magnetic head positioner assembly. In addition, FIG. 2 is an exploded perspective view showing the arrangement of the conventional magnetic head positioner assembly. Moreover, FIGS. 3A and 3B are plan and perspective views showing a magnetic head support member of the conventional magnetic head positioner assembly, respectively.
As shown in FIG. 1, the conventional magnetic head positioner assembly comprises magnetic head support members 510, an arm 520 for holding the magnetic head support members 510, and a movable coil 530 provided at the arm 520.
As shown in FIGS. 2, 3A, and 3B, the magnetic head support member 510 comprises a slider 512 of a floating or a contact type to which a magnetic head 511 is mounted, a gimbal spring 513 for supporting the slider 512, and a load beam 514 for providing a predetermined push load for the slider 512. In addition, the magnetic head support member 510 is fitted into a magnetic head support member mounting hole 528 provided on a holder arm 525 of the arm 520, via a boss 515a provided on a base plate 515.
FIG. 4 is a plan view showing the main portion of a conventional disk storage system. As shown in FIG. 4, a plurality of holder arms 525 which support the magnetic head support members 510 are integrated with the arm 520 at the proximal end thereof and mounted rotatably into the magnetic disk storage system via a rotatable bearing portion 527 provided on the arm 520.
At the end portion of the arm 520, there is formed a movable coil support portion 529 and the movable coil 530 is provided on the movable coil support portion 529. Moreover, the movable coil 530 and an external stationary magnetic circuit 560 on the side of the magnetic disk storage system constitute a voice coil motor (hereinafter referred to as the VCM). The VCM applies a predetermined drive current to the movable coil 530 and thereby generates a drive force to rotationally drive the arm 520 or the magnetic head support members 510 along a circular arc path in the direction of a seek operation (in the radial direction of the disks). This allows the positioning operation of the magnetic heads 511 to target tracks on the disks (the rotary actuator scheme).
Incidentally, the positioning operation mentioned above is divided into a seek operation (tracking) for moving the magnetic head 511 from the position of an arbitrary track to that of a target track and a follow operation (following) for allowing the magnetic head 511 to remain on the target track.
The magnetic heads 511 are prepared according to the number of recording media. In addition, each magnetic head support member 510 for individually supporting each magnetic head 511 is also swaged to each of the holder arms 525 according to the number of the magnetic heads 511. For example, two recording media provide four data recording surfaces on the both surfaces of the media. In this case, a total of four magnetic head support members 510 is swaged to the holder arms 525, respectively.
FIG. 5 is a side view showing the entire conventional magnetic head positioner assembly. FIG. 6 is an enlarged side view showing the region shown by P3 of FIG. 3. In the case where two recording media are available, the arm 520 comprises three holder arms 525 as shown in FIGS. 5 and 6. One magnetic head support member 510 is mounted to each of the holder arms 525a, 525a at the both ends of the stack of the holder arms 525. On the other hand, two magnetic head support members 510 are mounted to the middle holder arm 525b sandwiched by the two recording media 40 with each of the arm 520 being arranged to be opposite to each of the associated data recording surfaces of the recording media.
In addition, the conventional magnetic head positioner assembly is adapted to drive a plurality of magnetic heads 511 with one VCM at the same time. This provides insufficient positioning accuracy and particularly inaccurate tracking during a follow operation. Thus, as described above, this is making it difficult for the conventional magnetic head positioner assembly to cope with a high TPI system which requires a magnetic head positioning accuracy of 0.1 xcexcm or less.
Moreover, consider the case where a plurality of recording media are incorporated into a disk storage system to provide an increased capacity therefor. In this case, one magnetic head support member 510 is connected to each of the holder arms 525a, 525a at the both ends of the stack of the holder arms 525. In contrast, the middle holder arm 525b sandwiched by the recording media is connected with two magnetic head support members 510, 510. This will cause a difference in mass between the holder arms 525a and 525b, thereby presenting a problem of providing different vibration characteristics between the magnetic heads 511a, 511d at the both ends of the stack and the magnetic heads 511b, 511c at the middle portion of the stack.
This is conceivably resulted from a difference in mass caused by a difference in number of HGA (Head Gimbal Assembly) connected to the holder arms 525a, 525a located at the both ends of the stack and the middle holder arm 525b located at the middle portion of the stack. To improve this, it is commonly implemented to provide a dummy mass equivalent to the mass of the HGA for the holder arms 525a, 525a located at the both ends of the stack, thereby providing the same frequency characteristics for each of the magnetic heads. However, this allows the drive portion (the edge portion of the arms) to be provided with an additional excessive mass (dummy mass), thus presenting a problem of narrowing a control band due to the lowering of a resonance frequency to a lower band.
In addition, in a system with a plurality of recording media being implemented therein, the number of holder arms would increase as the number of recording media increases, thereby making the shape of the arm integrated therewith more complicated. This makes it difficult to form the arm. Furthermore, for example, forming the arm by cutting would present a problem of producing a great amount of cuttings and reducing in yield.
It is an object of the present invention to provide a disk storage system having a plurality of recording media implemented therein with a magnetic head positioner assembly which is provided with good vibration characteristics by eliminating a difference in frequency characteristics among the magnetic heads and which provides good productivity.
A magnetic head positioner assembly according to a first aspect of the present invention comprises a plurality of magnetic head support members for individually supporting magnetic heads, an arm comprising at least two, and a movable coil provided to said arm. Each of said arm units has two holder arms for individually supporting each of said magnetic head support members so as to position said magnetic head opposite to surface of recording media and a rotatable bearing portion for serving as a drive center of each of said holder arms, said arm units are combined and bonded with each other so as to align said bearing portion of all of arm units with each other and hold a space between neighboring holder arms of neighboring arm units
In the magnetic head positioner assembly according to the first aspect of the present invention, each of the holder arms to individually support the magnetic head support member. Thus, the equivalent mass of each magnetic head support member to be supported by the holder arms can be made uniform without an additional extra mass (a dummy mass). The head supporting rigidity can also be made uniform. Thus, this makes it possible to make the vibration characteristics uniform at the position of each of the magnetic heads.
Furthermore, the arm is split into arm units, each provided with two holder arms, to be combined and bonded therewith. Accordingly, the arm units can be formed individually, so that this arm provides more improved formation workability than an arm of an integrated type of which shape becomes complicated and therefore difficult to be formed with increasing number of recording media. In addition, this assures that the formation workability does not depend on the number of recording media (more specifically, the number of holder arms), thus providing a uniform formation workability while facilitating workability.
Furthermore, in this case, various types of arms can be constructed simply by setting a new combination of respective arm units according to the number of recording media. Thus, respective arm units of disk storage systems of various types can be shared and the cost for machining the various arms can be reduced. That is, fluctuations in the number of recording media can be coped with readily at low cost. This makes it possible to achieve a reduction in cost of various disk storage systems.
A magnetic head positioner assembly according to a second aspect of the present invention is the first magnetic head positioner assembly further comprises a plurality of fine actuators individually supported to each of said holder arm, each of said fine actuators comprising an actuator spring connected to said holder arm and a pair of piezoelectric devices for driving individually and infinitesimally said magnetic head support member.
In the magnetic head positioner assembly according to the second aspect of the present invention, functions equally as the first magnetic head positioner assembly. In addition, each of the holder arms supports individually each of the fine actuators. Thus, it is possible to make uniform the equivalent mass of each of the fine actuators supported by each of the holder arms without an additional extra mass (a dummy mass), and to keep uniform the head supporting rigidity. This thereby makes it possible to make uniform the vibration characteristics at the position of each of the magnetic heads in a magnetic head positioner assembly of the two stage actuator type.
A magnetic head positioner assembly according to a third aspect of the present invention is the second magnetic head positioner assembly further comprising said holder arms each being provided with the same portion in shape as the proximal portion of each of the actuator springs, with each of the holder arms and each of the fine actuators being bonded with each other at this same portion in shape.
In the magnetic head positioner assembly according to the third aspect of the present invention, functions equally as the second magnetic head positioner assembly. In addition, with a sufficient drive spacing being provided for the actuator springs, it is possible to provide the actuator springs with a vertical rigidity, a impact resistance, and durability at the time of loading/unloading. That is, a vertical rigidity can be assured at the magnetic head support member.
A magnetic head positioner assembly according to a fourth aspect of the present invention is one of the first to third magnetic head positioner assemblies in which number of said arm units is two, and each of said arm units has a movable coil support portion to support said movable coil at a portion opposite to said holder arm with respect to said bearing portion.
In the magnetic head positioner assembly according to the fourth aspect of the present invention, functions equally as one of the first to third magnetic head positioner assemblies. In addition, a movable coil (that is, a drive force generating source) can be provided at a plane orthogonal to the axial direction at the position of the rotational axis center of the arm. This makes it possible to apply the drive force uniformly to each of the holder arms and move each of the magnetic heads more positively in parallel to the surface of the recording media.
A magnetic head positioner assembly according to a fifth aspect of the present invention is one of the first to third magnetic head positioner assemblies in which number of said arm units is an odd number, and one of said arm unit has a movable coil support portion to support said movable coil at a portion opposite to said holder arm with respect to said bearing portion.
In the magnetic head positioner assembly according to the fifth aspect of the present invention, functions equally as one of the first to third magnetic head positioner assemblies. In addition, the movable coil support portion is formed only on the bonded portion of a pair of arm units, thereby making it possible to reduce the weight of the other arm unit by cutting off excessive weight of portions thereof having nothing to do with the strength and function of the arm. This allows the moment of inertial at the position of each of the magnetic heads to be reduced. Furthermore, for example, in a case of an even number of arm units (recording media), the pair of arm units having the movable coil support portion are arranged at center of the arm, thereby allowing the movable coil (that is, a drive force generating source) to be provided on a plane orthogonal to the axial direction at the position of the rotational axis center of the arm. This makes it possible to apply the drive force uniformly to each of the holder arms and move each of the magnetic heads more positively in parallel to the surface of the recording media.
A magnetic head positioner assembly according to a sixth aspect of the present invention is one of the first to third magnetic head positioner assemblies in which number of said arm units is an odd number, and one of said arm unit has a movable coil support portion to support said movable coil at a portion opposite to said holder arm with respect to said bearing portion.
In the magnetic head positioner assembly according to the sixth aspect of the present invention, functions equally as one of the first to third magnetic head positioner assemblies. In addition, the movable coil support portion is formed on one arm unit, thereby making it possible to reduce the weight of the other arm unit by cutting off excessive weight of portions thereof having nothing to do with the strength and function of the arm. This allows the moment of inertial at the position of each of the magnetic heads to be reduced. Furthermore, for example, in a case of an odd number of arm units (recording media), the one arm unit having the movable coil support portion is arranged at center of the arm, thereby allowing the movable coil (that is, a drive force generating source) to be provided on a plane orthogonal to the axial direction at the rotational axis center of the arm. This makes it possible to apply the drive force uniformly and move each of the magnetic heads more positively in parallel to the surface of the recording media.
A magnetic head positioner assembly according to a seventh aspect of the present invention is one of the first to sixth magnetic head positioner assemblies in which the two holder arms of each arm unit have each an arm base provided for the rotatable bearing portion and two arm plates bonded to the arm base and formed of a separate member of a thin plate.
In the magnetic head positioner assembly according to the seventh aspect of the present invention, functions equally as one of the first to sixth magnetic head positioner assemblies. In addition, the holder arm can be reduced in thickness and made higher in rigidity. That is, it is possible to provide the holder arms with an improved rigidity while reducing the thickness of the arm units or the arm, thus allowing the vibration characteristics at the position of the magnetic heads to be improved.
A magnetic head positioner assembly according to a eighth aspect of the present invention is the seventh magnetic head positioner assemblies in which said arm base has an edge portion on a recording medium side arranged in proximity of an outer periphery of the recording medium at a time of operation for service.
In the magnetic head positioner assembly according to the eighth aspect of the present invention, functions equally as the seventh magnetic head positioner assemblies. In addition, recording media can be implemented with a minimum necessary spacing being provided between the recording media and the arm (more specifically, the arm bases), thereby allowing the disk storage system to be reduced in size. Furthermore, it is also made possible to further reduce the disk storage system in size by shortening the distance between the edge portion of the arm base on the recording medium side and the center of rotation of the arm (more specifically, the arm base).
A magnetic head positioner assembly according to a ninth aspect of the present invention is one of the seventh and eighth magnetic head positioner assemblies in which the arm plates are each provided with through-holes.
In the magnetic head positioner assembly according to the ninth aspect of the present invention, functions equally as one of the seventh and eighth magnetic head positioner assemblies. In addition, the arm plate (holder arm) can be reduced in weight, that is, a decrease in rigidity of the arm plate can be prevented while the weight of inertia is being reduced at the time of operation for service. The vibration characteristics at the position of the magnetic heads can be thereby improved while the arm is kept reduced in thickness. Furthermore, the through-holes can be formed in the same process as the formation of the main body of the arm plate, thereby making it possible to realize a reduction in weight at low cost.
A magnetic head positioner assembly according to a tenth aspect of the present invention is one of the seventh and eighth magnetic head positioner assemblies in which the arm plates are less in thickness at a central portion thereof than at an outer rim portion.
In the magnetic head positioner assembly according to the tenth aspect of the present invention, functions equally as one of the seventh and eighth magnetic head positioner assemblies. In addition, the arm plate (holder arm) can be reduced in weight, that is, a decrease in rigidity of the arm plate can be prevented while the weight of inertia is being reduced at the time of operation for service. The vibration characteristics at the position of the magnetic heads can be thereby improved while the arm is kept reduced in thickness.
A magnetic head positioner assembly according to a eleventh aspect of the present invention is one of the seventh to tenth magnetic head positioner assemblies in which the arm plates are each provided with flange portions on the both end portions in the longitudinal direction thereof.
In the magnetic head positioner assembly according to the eleventh aspect of the present invention, functions equally as one of the seventh to tenth magnetic head positioner assemblies. In addition, the arm plate (holder arm) can be further improved in rigidity by providing the flanges thereto. Alternatively, the rigidity required can be assured while the arm plate is further reduced in thickness, thereby allowing the vibration characteristics at the position of the magnetic heads to be improved. Moreover, the arm plate (holder arm) reduced in weight can be prevented from being reduced in rigidity due to the reduction in weight or can be improved in rigidity. This allows the weight of inertia to be reduced at the time of operation for service and the rigidity to be improved as well, thereby making it possible to improve the vibration characteristics at the position of the magnetic heads.
A magnetic head positioner assembly according to a twelfth aspect of the present invention is one of the seventh to eleventh magnetic head positioner assemblies in which a boss provided on the arm plate and a mounting hole provided to the arm base allow the arm plate and the arm base to be fitted to each other.
In the magnetic head positioner assembly according to the twelfth aspect of the present invention, functions equally as one of the seventh to eleventh magnetic head positioner assemblies. In addition, the boss serves for positioning between the arm plate and the arm base, thus facilitating bonding therebetween. That is, dimensions can be easily controlled at the time of bonding the arm plate to the arm base, thereby allowing the assembling workability to be improved.